Papers by Keyword: Nanoscale

Abstract: This research signifies an attempt to apply composite coating by co-deposition coating and assessing, enhancement the Nickel coatings features, by adding the particles of silicon-carbide to solution of electrodeposited. Stainless steel specimens have been subject to electroplating coating utilizing Nickel and nanosilicon carbide particles (70-100 nm) with various amounts (16, 24, 32 and 40) g/L. After coating, the specimens were tested by SEM, AFM, impeded in a solution with 3.5 percent NaCl to investigate the corrosion performance. Then testing the microhardness, and wear resistance. Results obtained from this work showed a great reduction in corrosion currents caused by adding of inert nanoparticles. These enhancements had been detected on all conducted tests for corrosion and wear.

Abstract: Nanotechnology has contributed significantly to different subfields of the construction industry, including asphalt pavement engineering. The improved properties and new functionalities of the nanomaterials have provided different desired properties of asphalt. In this study, the effectiveness of multi-walled carbon nanotubes (MWCNT) in resisting the oxidation of polymer-modified asphalt was measured. A total of three different percentages (0.5%, 1%, and 1.5%) of MWCNT were used to modify the Styrene-Butadiene (SB) and styrene–butadiene–styrene (SBS) modified asphalt (4% and 5%). The laboratory oxidized asphalt samples were evaluated by an atomic force microscopy machine. The oxidation of the polymer-MWCNT modified asphalt is measured by simulating the existing functional group of the asphalt and as a function of the adhesive force. It is observed that the use of MWCNT in SB and SBS can increase the resistance to oxidation.

Abstract: This paper starts from the leakage currents through the gates of the last MOSFET generations and propose a related structure, which can be inherently included as parasitic device in any future MOSFET sub-22nm or can be deliberated fabricated to induce its own behavior. This structure is abbreviated in this paper by p-NOI (planar-Nothing On Insulator) and it can be simply produced by the planar Si-technology. Its concept is derived from the NOI (Nothing On Insulator) concept, but replaces the vacuum with oxide. The conduction mechanism is based on a thin oxide tunneling, under the Fowler-Nordheim's law. The current flow occurs from a source to a lateral drain, without an inversion channel and without a lateral pn junction, as in the MOSFET case. A similar investigated device by other authors is a fabricated MIM (Metal-Insulator-Metal) structure, which is compared with the actual p-NOI simulation. Finally, a dual gate p-NOI device is investigated. The depletion-accumulation transition is captured by the static I-V static characteristics. Using two steps of oxide, of 2nm and 10nm, a second planar-NOI structure with three terminals was studied. The (G) terminal is associated to a Gate and the (S) terminal is associated to a Source of a Field Effect Transistor. Some particular applications as diode or transistor are emphasized versus the gate biasing regime.

Abstract: This paper aims to give an overview on some relevant aspects of the characterization of the SiO₂/4H-SiC interface, considering the properties of this system both at the interface and inside the insulator. Nanoscale scanning probe microscopy (SPM) techniques were used to get insights on the homogeneity of the SiO₂/SiC interface electrical properties upon metal-oxide-semiconductor (MOS) processing. On the other hand, capacitance and current measurements as a function of time were employed to investigate trapping states in MOS structures in the SiO₂/4H-SiC system. In particular, time-dependent gate current measurements gave information on the near interface oxide traps (NIOTs) present inside the SiO₂ layer. The impact of the observed trapping phenomena on SiO₂/SiC metal oxide semiconductor field effect transistors (MOSFETs) operation is discussed.

Abstract: We study the influence of chain length of our 1D model of thermal transistor on thermal amplification factor. Here, we varied the length of drain and source segments for different simulation experiment and found that the maximum value of thermal amplification factor influenced with chain length. The thermal amplification factor of the thermal transistor is found to be dependent on gate temperature. We also calculated the switching efficiency and working region of the thermal transistor and better results are obtained in comparison to previous study.

Abstract: This paper presents a three-dimensional multiscale computational model, which is proposed to combine the simplicity of FEM model and the atomistic interactions between two solids. A significant advantage of the model is that atoms are populated in the contact regions, which saves significant computation time compared to fully MD simulations. The model is used in the case of asperity contact. The normal displacement, contact radius and pressure distribution are compared with those from Hertz’s solution and atomistic simulations in the literature. Some important features of nanoscale contacts obtained by MD simulations can be caught by the model with acceptable accuracy and low computational cost.

Abstract: In binary systems Kirkendall shift is a well-known phenomenon. We investigated nanoscale diffusion in the framework of a recently published continuum model [Erdélyi and Schmitz, Acta. Mater. 60 (2012) 1807]. In thin films the usual vacancy creation and annihilation mechanisms, leading to the Kirkendall shift on larger scales, cannot operate in the same way. On this length-scale the characteristic distances between vacancy sinks and sources can be comparable to the dimension of the sample, causing differences in the development of the Kirkendall effect. Our group recently reported results in simulating nanoscale Kirkendall shift. In present work we show how using conventional method for velocity reconstruction used in multifoil experiments can be misleading if the distribution of vacancy sinks and sources is not uniform.

Abstract: Investigations on carburized layers phase composition are usually made ​​by optical microscopy, electron microscopy and X-ray diffraction. A microstructure consisting in different proportions of superior bainite, inferior bainite, martensite and retained austenite was found after carburizing in paste of the 21NiCrMo2 steel which has appropriate bainitic hardenability. The investigations carried out on 21NiCrMo2 steel samples, carburized in paste with additions of about 10% Ce, highlighted a significant change of phase proportions ratio in the carburized layer resulting in an important increasing of the lower bainite ratio. It was also observed, that the carburized layer case depth obtained in the carburizing paste with Ce additions does not significantly differ in relation to that attained in the carburizing paste without Ce additions but the microhardness increases considerably. The reason is connected also to the presence of Ce carbide identified by X-ray diffraction in the carburized layer. The Ce hard affinity towards oxygen and its influence on bainitic hardenability increasing is well known and adopted, however neither Ce transfer mechanism from carburizing paste to the carburizing layer and nor the effects of its high affinity to oxygen (for example) are not addressed in this particular case. The present study proposes a possible transfer mechanism of Ce in the carburized layer and an explanation of the consequences of Ce hard affinity towards oxygen on the phase composition of the carburized layer. Nanoscale iron oxides such as wüstite, magnetite and maghemite were identified in the surface of the carburized layer by Mössbauer spectrometry.

Abstract: A nanocantilever bending method is developed to investigate the interface cracking in multilayered nanoscale materials basing on the technology of the focused ion beam (FIB) and the transmission electron microscopy (TEM). With FIB, a nanocantilever specimen consisting of 20-nm-thick copper (Cu) layer and 500-nm-thick silicon nitride (SiN) layer on a silicon (Si) substrate is fabricated from a macroscale multi-layered material (Si/Cu/SiN) with the proposed method. By using a minute loading apparatus, the loading experiment is conducted in TEM, and the crack initiation at the edge of Cu/Si interface in different specimens is in situ observed. The critical stress fields at crack initiation are analyzed with the finite element method, and both normal and shear stresses concentrate at the region of 100 nm from the interface edge in all specimens. In addition, the normal stress is much larger than the shear one. A close observation on stress fields shows that the normal stress field at the area 20 nm–30 nm away from interface edge produces the local criterion for crack initiation at the edge of Cu/Si interface in nanoscale components.

Abstract: Based on classical elasticity theory, the effects of surface stresses on the nanosized contact problem in an elastic half-plane which contains a nanocylindrical hole are analyzed. Meanwhile, the effects of surface energy of the contact nanosized surface are considered. The complex variable function method is applied to derive the fundamental solution of the contact problem. As example, the deformation induced by a distributed traction of cosine function on the nanosized surface is analyzed in detail. The results tell some interesting characteristics in contact mechanics, which are different from those in classical elasticity theory.